Messier 46 (also known as M 46 or NGC 2437) is an open cluster in the constellation of Puppis. It was discovered by Charles Messier in 1771. Dreyer described it as "very bright, very rich, very large." M46 is about 5,500 light-years away.[1] There are an estimated 500 stars in the cluster, and it is thought to be some 300 million years old.[2]

The planetary nebulaNGC 2438 appears to lie within the cluster near its northern edge (the faint smudge at the top center of the image), but it is most likely unrelated since it does not share the cluster's radial velocity.[1][3] It is an example of a superimposed pair possibly similar to that of NGC 2818.[1][4]

M46 is located close by to another open cluster, Messier 47.[2] M46 is about a degree east of M47 in the sky, so the two fit well in a binocular or wide-angle telescope field.